Generally, emergency service calls (e.g., 911 calls) may originate over a wireline or fixed access network (e.g., including landlines) or over a wireless or mobile access network (e.g., including wireless links). For all such emergency service calls, location information regarding the location of the calling user device is determined to assist the emergency service providers. In North America, systems for determining location information are called Automatic Location Identification (ALI) systems.
The location information provided to the emergency service providers for wireline calls is usually contained in a database, which links the line number of the calling user device to subscriber information of the user, which includes the location information. The line number of the user device may be provided (e.g., via signaling) by Automatic Number Identification (ANI). The location information is static and typically includes a street address (“civic address location”) that is permanently associated with the line number. Limitations of conventional ALI systems limit the emergency service providers to use of the civic address location in this scenario.
In contrast, the location information provided to the emergency service providers for non-wireline or wireless calls (e.g., mobile calls) must be determined dynamically based on the location of the calling user device at the time the call is made. For example, calls to emergency service providers from mobile devices using a mobile service provide a routing and query key called pseudo-ANI (pANI), which identifies the originating network operator and provides a coarse indicator for the geographical area allowing routing decisions to be made. In cellular networks, for example, the pANI is used by ALI systems to identify and query a mobile location center (MLC) in the operator's cellular network in order to obtain a general location of the mobile device. This location is usually sufficiently accurate for purposes of dispatching emergency responders. The location information is provided dynamically and typically includes an area defined by latitude and longitude (“geodetic location”). Limitations of conventional ALI systems limit the emergency service providers to use of the geodetic location in this scenario.
Internet calling applications, such as Voice over IP (VoIP), enable a user device to operate according to either a fixed access network service or a mobile access network service, using a common line number for either. Internet calling applications thus create a problem for ALI systems, which need to know when to use static location information associated with access to a fixed access network and when to use dynamic location information associated with access to a mobile access network.
According to a representative embodiment, a method is provided for processing emergency service calls from a user device to a PSAP, the user device having an associated line number and being configured to originate calls from a fixed access network and a mobile access network. The method includes determining whether a call from the user device originates from a home location in a fixed access network. When the call is determined to have originated from the home location in the fixed access network, the call is routed to the PSAP, where a location of the user device is determined based on the Automatic Number Identification (ANI) included in signaling associated with the call. When the call is determined not to have originated from the home location in the fixed access network, adding pseudo-ANI to signaling associated with the call and routing the call to the PSAP, where the location of the user device is determined based on the pANI.
According to another representative embodiment, a system for processing calls for emergency services from a user device having an associated line number includes a public safety answering point (PSAP) switch and an Automatic Location Identification (ALI) server. The PSAP is configured to receive a call for emergency services from a switch in communication with a fixed access network and a mobile access network. The call includes Automatic Number Identification (ANI), and no pseudo-ANI (pANI), when the call originates from the user device at a home location in the fixed access network, and the call includes pANI when the call originates from the user device at a remote location in the fixed access network or at a location in a mobile access network. The ALI server is connected to the PSAP switch and configured to determine a location corresponding to the user device based on the ANI when the call originates from the user device at the home location in the fixed access network, and based on the pANI when the call originates from the user device at the remote location in the fixed access network or at the location in the mobile access network.
According to another representative embodiment, a system for processing calls for emergency services from a user device having an associated line number includes a network switch and first and second location servers. The network switch is configured to receive emergency service calls from a user device to a PSAP originating in a fixed access network and a mobile access network, to include ANI and no pANI in call signaling for the emergency service calls that originate from the user device at a home location in the fixed access network, to include pANI in the call signaling for the emergency service calls that originate from the user device at a remote location in the fixed access network or at a location in a mobile access network, and to route the emergency service calls to the PSAP. The first location server is in the fixed access network, and is configured to determine a location of the user device in the fixed access network in response to a query from an ALI server in the PSAP for emergency service calls from the user device originating at a remote location in the fixed access network, and to provide the determined location to the ALI server. The second location server is in the mobile access network, and is configured to determine a location of the user device in the mobile access network in response to a query from the ALI server for emergency service calls from the user device originating in the mobile access network, and to provide the determined location to the ALI server. The location corresponding to the user device is determined based on the ANI when the call originates from the user device at the home location in the fixed access network.